Copper alloy



United States Patent Ofitice 3,357,824 Patented Dec. 12, 1967 3,357,824 COPPER ALLOY Matti J. Saarivirta, Marquette, Mich, assignor to Calumet & Hecla, Inc, a corporation of Michigan No Drawing. Filed July 6, 1965, Ser. No. 469,858 4 Claims. or. 75-453) ABSTRACT OF THE DISCLOSURE A copper alloy with chromium, zirconium and arsenic with the copper being either initially oxygen free or deoxidized, the alloy having a fine uniform grain structure with a resulting high degree of ductility and the presence of the chromium with the zirconium and arsenic increasing the fine grain temperature limit to as much as 1000 C. from about 900 C. without chromium which of course further promotes a fine grain structure in the alloy,

This invention relates to high conductivity copper alloys having small and uniform grain size which gives superior ductility.

One of the features of this invention is to provide an improved copper base alloy having a small and substantially uniform grain size with resulting high degree of ductility while still achieving high strength, hardness and electrical and thermal conductivity, all at both room and elevated temperatures, in which the copper which is either initially oxygen free copper or deoxidized copper is alloyed with chromium, zirconium and arsenic.

Another feature of the invention is to provide such an alloy in which the chromium is present between a small but measurable amount and about 2%, the zirconium is present in an amount from about ODS-1.5% and the arsenic is present in an amount between about 0.020.8%.

Another feature of the invention is to provide such an alloy in which the amount of chromium is about 0.5- 1.0%, the amount of zirconium is about 0.2O.5% and the amount of arsenic is about 0.10.25% with the zirconium and arsenic being combined with each other in the alloy in about a 2:1 weight ratio with the small and substantially uniform grain size being about 0.01-0.015 mm.

The high conductivity, small grain copper alloy of this invention comprises chromium in an amount between a small but measurable amount and about 2%, zirconium in an amount from about 0.051.5%, and arsenic in an amount of about 0.020.8%, with the remainder of the alloy essentially copper. Other minor amounts of ingredients such as nickel, iron, silicon, phosphorus, etc., may be present, if desired. The percentages and proportions herein are by weight.

The alloys that are especially preferred contain initially oxygen free copper or deoxidized copper and about 0.5- 1.0% chromium, about 0.2O.5% zirconium and about 0.10.25% arsenic.

The copper of the alloy contains the lowest amount possible of oxygen. This can be either initially oxygen free copper which is ordinarily produced in a reducing atmosphere, although copper produced in an inert atmosphere or a vacuum may also be considered as initially oxygen free, or copper that has been deoxidized with such well known deoxidizers as phosphorus, silicon, lithium, calcium, calcium boride or the like which combine with the oxygen substantially to eliminate it.

The alloys of this invention have been found to be useful in manufacturing resistance welding electrodes as well as electrical and electronic components generally.

The zirconium and arsenic appear to combine in the proportions of about 2 parts by weight of zirconium to each part by weight of arsenic and the dispersed particles of this combination result in the copper alloy having a fine and uniform grain structure. This fine grain structure makes the copper alloy of this invention very ductile.

The presence of the chromium in the alloy increases the response of the alloy to precipitation hardening and gives increased hardness and tensile strength. In addition, the chromium increases the fine grain temperature limit from a maximum of about 900 C. without the chromium to as much as 1000 C. with the chromium. Thus the alloy will have the desired fine grain without the chromium, but the presence of chromium is preferred.

Microscopic examination of cast alloys of this invention indicate that there are two phases present in the alpha matrix. One of these appears to be finely dispersed zirconium-arsenide in combined form, as discussed above, and the other phase appears to be chromium rich particles that are larger in size than the zirconium-arsenide.

The new alloy may be fully annealed by solution heat treatment in a non-oxidizing atmosphere (reducing or inert). This is a well known procedure in which the alloy is heated to a temperature between about 9001000 C. and then cooled by rapid quenching.

The solution heat treated alloy of this invention responds excellently to precipitation or age hardening. This is generally achieved by reheating the quenched alloy for one hour or more at about 300-600 C. for the one or more hours aging. In general, the higher the temperature the shorter the aging time. In practice, excellent precipitation hardening conditions have been to reheat to about 500 C. for about 2 hours.

This precipitation hardening strengthens the alloy while at the same time increasing the thermal and electrical conductivity.

The strength and hardness of the alloy can be further increased by cold working in the usual manner, This cold working can be performed as an intermediate step invention not only has a good response to precipitation hardening, as indicated, but also can be produced with a cipitation hardening as desired.

The small grain (about 0.01-0.015 mm.) alloy of this invention not only has a good response to precipitation hardening ,as indicated, but also can be produced with a minimum electrical conductivity of IACS (International Annealed Copper Standard), The alloy can also be produced with a tensile strength up to about 84,000 p.s.i. and about 20-26% elongation in 2 inches. These properties are developed during solution heat treatment at temperatures below about 1000 C., preferably about 900980 C.

A very important factor in providing small and uniform grain size is the substantially uniform distribution of the extremely fine zirconium-arsenic combination particles in the alpha matrix of the alloy. Solution heat treatment at 950980 C. and subsequent aging for at least one hour at about 500 C. results in tensile strength of 54,000- 61,000 p.s.i., about 2326% elongation in 2 inches, about -114 VPN hardness and about 82-87% IACS electrical conductivity. If the alloy is cold worked as an intermediate step between solution heat treatment and precipitation hardening,'a tensile strength of at least about 84;000"p;s.i. can be achieved. In addition, the alloys of this invention are easy to cast and have excellent hot and cold workability characteristics.

In the following tables various examples of alloys of this inventionand alloys tested are presented. In certain examples, as indicated, the copper was phosphorus deoxidized lake copper. A typical analysis is silver 0.022%, lead, 0.005%, iron 0.001%, nickel 0.008% and phosphorus 0.02% with the remainder being copper. Also, certain of the examples, as indicated, used initially oxygen free copper. A typical analysis here is lead 0.0003%, iron 0.0005 nickel 0.0006% and phosphorus less than 0.0003% with the remainder being copper.

In each example the copper was melted first and then the chromium was added. After the chromium had become completely dissolved in the copper melt the other alloying ingredients were added and homogeneously mixed. 500-1000 gram castings were then made at casting temperatures of 1ll01200 C. in graphite and cast iron molds with each 1000 gram casting being about 0.75 inch in diameter by 12 inches long and the 500 gram castings being about 0.5 inch in diameter by 12 inches long. Dur- 4 Table II In the following Table 11 Examples 1-5 illustrate the affects of different amounts of chromium, as indicated in the first column, on the physical characteristics of an alloy having added thereto, in addition to the chromium and copper, 0.5% zirconium and 0.25% arsenic. The alloy which was in the form of 0.146 inch diameter wire was solution heat treated at 970 C. in each instance for minutes, quenched in water and aged at 500 C. for 2 hours.

In Example 6 the alloy was made with 1% chromium, 0.85% Zirconium and 0.35% arsenic.

In Example 7 the amount of zirconium was 1% and of arsenic 0.5%. The alloys of Examples 6 and 7 were heat treated, quenched and aged as indicated immediately above.

In Example 8 the alloy was produced with 1% chromium, 0.5% zirconium, 0.25 arsenic, 0.1% nickel and 0.03% silicon. The alloy was heat treated and precipitation hardened as indicated above.

Example Cr. Percent Tensile Strength, p.s.i.

Elong, Percent in 2 in.

Hardness Eleo. Cond.,

Percent IAOS Average Grain Size, mm.

VPN Rb ing the melting and the casting the melts were maintained under non-oxidizing conditions. Thus, in most instances, they were surrounded by an atmosphere of an inert gas, particularly argon.

Table I The following are the compositions of typical alloys as produced, with Examples 1-14 using phosphorus deoxidized lake copper and Examples 15-21 using initially oxygen free copper.

Table III Tensile Elong., Hardness, Average Elee. Cond., Example Treatment Strength, percent VPN Grain percent p.s 1 1n 2 in. Size, mm. IACS Solution annealed at 850 C 35,000 27 56 0. Solution annealed at 900 C... 36,000 34 51 0. Heat treated 49, one 23 93 0. 01 so Solution annealed at 930 C 35,000 31 56 0. 01 47 Heat treated 54, 000 23 100 0. 01 87 Solution annealed at 975 0... 38,000 33 48 0.01 43 Heat treated 64, 000 23 126 0.01 81 Example No. Chromium, Zirconium, Arsenic, percent percent percent 60 Table IV .17 .55 .25 .25 .55 .25 .37 .55 .25 55 .25 The following Table IV illustrates the improved tensile .23 :28 strength properties of the alloy of this invention at eleg vated temperatures as compared with the ordinary cop- :5 I per-chromium and copper-zirconium alloys. In each exg; g; ample, the alloy in the form of 0.146 inch diameter wire 1.38 .55 .25 was solution annealed at the temperature indicated, then .90 .85 .35 1.02 1.10 cold drawn to 0.081 inch diameter (a 72% reduction) and recipitation hardened at 475 C. for 1 hour. Each .25 .55 9 .15 1 2 alloy was tested at the temperature indicated after being held at this temperature for a 1 hour stabilizing period. :82 I55 125 Example 5 has the same composition as Example 4 and Examples 7, 8 and 9 the same as Example 6.

Testing Ultimate Example Alloy and Treatment Tempem- Tensile ture, 0. Strength,

Copper, 0.64% Cr, 0.5% Zr, 400 60, 000

0.22% As Solution annealed 080 C. Copper, 0.70% CI 400 45, 000 Copper, 0.15% Z1 .r 400 50, 000 Copper, 0.64% Cr, 0.5% Zr, 400 58,000

0.22% As Solution annealed at 970 C. Solution annealed at 1,000 C 500 56, 000 Copper, 0.8% Cr, 0.5% Zr, 400 57, 000

0.25% As Solution annealed at 970 C. Solution annealed at 1,000 O 500 54, 000 do 400 05,000 ..do 500 58,000 Copper, 0.7% Cr. Solution 400 53,000

annealed at 1,020 0. Copper, 0.9% Cr, Solution 400 55,000

annealed at 1, z C. do 500 49, 000

The above examples with the test results recorded in the tables illustrate graphically the improved properties of the alloys of this invention. The chief advantage of the alloys of this invention is the improved ductility due to small and uniform grain size. This is accomplished while maintaining high tensile strength and high conductivity.

Having described my invention as related to the embodiments set out herein, it is my intention that the invention be not limited by any of the details of description, unless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claims.

I claim:

1. A copper base alloy having a small and substantially uniform grain size with resulting high degree of ductility, as well as high strength, hardness and conductivity at room and elevated temperatures, consisting essentially of chromium between a small but measureable amount and about 2%, from about 0.05-1.5% of zirconium and about 0.02-0.8% of arsenic, and the balance a member of the class consisting of initially oxygen free copper and deoxidized copper, the percentages being by weight of the alloy.

2. A copper base alloy having a small and substantially uniform grain size with resulting high degree of ductility, as well as high strength, hardness and conductivity at room and elevated temperatures consisting essentially of chromium between a small but measurable amount and about 2%, from about ODS-1.5% of zirconium and about 002-0.8% of arsenic, said zirconium and arsenic being combined with each other and present in the copper in the form of dispersed particles, and the balance a member of the class consisting of initially oxygen free copper and deoxidized copper, the percentages being by weight of the alloy.

3. A copper base alloy having a small and substantially uniform grain size with resulting high degree of ductility, as well as high strength, hardness and conductivity at room and elevated temperatures, consisting essentially of chromium between a small but measurable amount and about 2%, from about ODS-1.5% of zirconium and about 0.02-0.8% of arsenic, and the balance a member of the class consisting of initially oxygen free copper and decxidized copper, the grain size of said alloy being between about 0.010.015 mm., the percentages being by Weight of the alloy.

4. A copper base alloy having a small and substantially uniform grain size with resulting high degree of ductility, as well as high strength, hardness and conductivity at room and elevated temperatures, consisting essentially of about 0.20.5% of zirconium and about 0.1-0.25% of arsenic combined in about a 2:1 Weight ratio and about 0.51.0% of chromium, and the balance a member of the class consisting of initially oxygen free copper and deoxidized copper, said alloy having a substantially uniform grain size between about 0.01-0.015 mm., an IACS electrical conductivity of at least about 80%, and a tensile strength of up to about 84,000 psi. after solution heat treatment and precipitation hardening, the percentages being by Weight of the alloy.

References Cited UNITED STATES PATENTS 2,842,438 7/1958 Saarivirta et al. 153 3,107,998 10/1963 Saarivirta 75-153 3,143,442 8/1964 Watts 75-153 X 3,194,655 7/1965 Pels 75-153 X CHARLES N. LOVELL, Primary Examiner. 

1. A COPPER BASE ALLOY HAVING A SMALL AND SUBSTANTIALLY UNIFORM GRAIN SIZE WITH RESULTING HIGH DEGREE OF DUCTILITY, AS WELL AS HIGH STRENGTH, HARDNESS AND CONDUCTIVITY AT ROOM AND ELEVATED TEMPERATURES, CONSISTING ESSENTIALLY OF CHROMIUM BETWEEN A SMALL BUT MEASUREABLE AMOUNT AND ABOUT 2%, FROM ABOUT 0.05-1.5% OF ZIRCONIUM AND ABOUT 0.02-0.8% OF ARSENIC, AND THE BALANCE A MEMBER OF THE CLASS CONSISTING OF INITIALLY OXYGEN FREE COPPER AND DEOXIDIZED COPPER, THE PERCENTAGES BEING BY WEIGHT OF THE ALLOY. 